LS6 MORPHOLOGY AXD EVOLUTION
between the two heads. It is inserted into the middle third of the outer border of the shaft of the radius. In the Gibbon it is also inserted into the front of the radius.
The flexor carpi radialis in the Chimpanzee arises from the internal condyle of the humerus and the greater part of the shaft of the radius. Fibres also pass into it from the pronator radii teres and flexor sublimis digitorum. It passes through a tube in the anterior annular ligament, and is inserted into the palmar aspect of the bases of the second and third metacarpals. Hepburn (83) states that it is attached by a fibrous septum to the radius ^on the inner aspect of the pronator teres in all Apes except the Chimpanzee.
The flexor carpi ulnaris is similar in the Apes and Man. The ulnar nerve enters the forearm between its heads of origin. It is a large muscle.
The flexor sublimis digitorum in the Chimpanzee arises from the humerus, radius, ulna and other flexor muscles. The condvlar head fuses with the flexores
carpi radialis and ulnaris; it sends tendons to the ring and little fingers. The coronoid head quickly ends in a tendon to the index finger. ' The middle finger receives its tendon from a muscle arising^from the lower two-thirds of the shaft of the radius. The tendons split and are inserted as in Man. Hepburn (83) points out that the arrangements are similar to those in the Gorilla and Orang. The variations in the Chimpanzee have been described by Bland-Sutton (402), Dwight (325), Champneys (318), Moore (363) and Macalister (350).
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Flexor Longus Pollicis.—This muscle is absent in some Gorillas; but when it is present, as in the Chimpanzee, Orang and some Gorillas, it is merely a fine